"Rapid-impact interventions": how a policy of integrated control for Africa's neglected tropical diseases could benefit the poor

Bayesian risk maps for Schistosoma mansoni and hookworm mono-infections in a setting where both parasites co-exist

There is growing interest in the use of Bayesian geostatistical models for predicting the spatial distribution of parasitic infections, including hookworm, Schistosoma mansoni and co-infections with both parasites. The aim of this study was to predict the spatial distribution of mono-infections with either hookworm or S. mansoni in a setting where both parasites co-exist. School-based cross-sectional parasitological and questionnaire surveys were carried out in 57 rural schools in the Man region, western Côte d'Ivoire. A single stool specimen was obtained from each schoolchild attending grades 3-5. Stool specimens were processed by the Kato-Katz technique and an ether concentration method and examined for the presence of hookworm and S. mansoni eggs. The combined results from the two diagnostic approaches were considered for the infection status of each child. Demographic data (i.e. age and sex) were obtained from readily available school registries. Each child's socio-economic status was estimated, using the questionnaire data following a household-based asset approach. Environmental data were extracted from satellite imagery. The different data sources were incorporated into a geographical information system. Finally, a Bayesian spatial multinomial regression model was constructed and the spatial patterns of S. mansoni and hookworm mono-infections were investigated using Bayesian kriging. Our approach facilitated the production of smooth risk maps for hookworm and S. mansoni mono-infections that can be utilized for targeting control interventions. We argue that in settings where S. mansoni and hookworm co-exist and control efforts are under way, there is a need for both mono- and co-infection risk maps to enhance the cost-effectiveness of control programmes.

FLOTAC: a new sensitive technique for the diagnosis of hookworm infections in humans

Hookworms infect more than 10% of the world's population, but current diagnostic tools have drawbacks. Our objective was to compare the diagnostic performance of three methods (Kato-Katz, ether concentration and FLOTAC techniques) for hookworm diagnosis. Stool samples were obtained from 102 schoolchildren in Côte d'Ivoire. First, a duplicate 41.7mg Kato-Katz thick smear was prepared. Next, a small portion of stool (mean weight 1.8g) was preserved in sodium acetate-acetic acid-formalin and forwarded to a European laboratory. These samples were split in three parts, one processed by an ether concentration technique and two by the FLOTAC technique. All samples were examined by experienced technicians for hookworm eggs using light microscopy. The observed hookworm prevalences as assessed by the FLOTAC, Kato-Katz and ether concentration techniques were 65.7%, 51.0% and 28.4%, respectively. Considering the combined results as the diagnostic 'gold' standard, the FLOTAC technique had a sensitivity of 88.2% compared with 68.4% for the Kato-Katz and 38.2% for the ether concentration techniques. The Kato-Katz method resulted in a significantly higher mean number of eggs per gram of stool (155.8 EPG) compared with the FLOTAC (37.7 EPG) and ether concentration (5.7 EPG) methods. The FLOTAC method shows promise as an important new tool for individual hookworm diagnosis and for rigorous monitoring of helminth control programmes. [Clinical Trial No. ISRCTN21782274].

Recent progress in integrated neglected tropical disease control

Three years have passed since the publication of the first of a series of policy papers, which first highlighted the under-appreciated global burden of the neglected tropical diseases (NTDs) and then outlined a rationale for linking vertical control strategies for the seven most prevalent NTDs in a cost-effective pro-poor package of preventive chemotherapy. Since then, global advocacy for these conditions has increased and, with it, new funds for scale-up of integrated NTD control in sub-Saharan Africa. Recent speeches by the Director General of the World Health Organization at regional meetings have referred to NTDs as important global health priorities (www.who.int/dg/speeches/2007). Outlined here is a summary of the recent progress in global efforts to integrate NTD control, with an emphasis on the challenges that lie ahead.

Deworming drugs for treating soil-transmitted intestinal worms in children: effects on growth and school performance

BACKGROUND

In areas where intestinal worm infections occur, the World Health Organization recommends treating all school children at regular intervals with deworming drugs to improve growth and school performance. The evidence base for this policy needs to be established for countries to commit resources to implement these programmes.

OBJECTIVES

To summarize the effects of deworming drugs used to treat soil-transmitted intestinal worms (nematode geohelminths) on growth and school performance in children.

SEARCH STRATEGY

In May 2007, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2007, Issue 2), MEDLINE, EMBASE, LILACS, mRCT, and reference lists.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials (RCTs) comparing deworming drugs for geohelminth worms with placebo or no treatment in children aged 16 years or less, reporting on growth, nutritional status, school performance, or cognition tests.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials and evaluated methodological quality; one author extracted data, and another checked a sample. Continuous data were analysed using the weighted mean difference (WMD) with 95% confidence intervals (CI). The random-effects model (RE model) was used in the presence of statistically significant heterogeneity.

MAIN RESULTS

Thirty-four RCTs, including six cluster-RCTs, met the inclusion criteria. Four trials had adequate allocation concealment, and three cluster-RCTs failed to take design effects into account in their analysis. Weight increased after one dose of a deworming drug (WMD 0.34 kg, 95% CI 0.05 to 0.64, RE model; 2448 children, 9 trials); however, there was considerable heterogeneity between trials that was not explained by background intestinal worm infection or intensity. A meta-analysis of multiple dose trials reporting on outcomes within a year of starting treatment showed no significant difference in weight gain (1714 children, 6 trials); however, one cluster-RCT did show effects on weight at one year in a subgroup analysis. In the seven multiple dose trials with follow up beyond 12 months, only one showed a significant increase in weight. Six of seven trials reported clear data on cognitive tests and school performance: five reported no significant effects, and one showed some improvements in three out of 10 cognitive tests.

AUTHORS' CONCLUSIONS

Deworming drugs used in targeted community programmes may be effective in relation to weight gain in some circumstances but not in others. No effect on cognition or school performance has been demonstrated.

Helminth infections and risk factor analysis among residents in Eryuan county, Yunnan province, China

Whilst infections with soil-transmitted helminths are common across China, the public-health significance of Schistosoma japonicum and food-borne helminths is more focalized. Only few studies have investigated the local epidemiology of helminth infections in rural China, including risk factor analysis. We collected stool and blood samples from 3220 individuals, aged 5-88 years, from 35 randomly selected villages in Eryuan county, Yunnan province, China. Stool samples were subjected to the Kato-Katz technique and examined for helminth eggs. Blood samples were tested for Trichinella spp., S. japonicum and cysticerci-specific antibodies. Data on individual and family-level risk factors were collected using questionnaires. The prevalence of Ascaris lumbricoides, Taenia spp., Trichuris trichiura and hookworms was 15.4%, 3.5%, 1.7% and 0.3%, respectively. The seroprevalence of Trichinella spp. was 58.8% and that of cysticercosis 18.5%. The egg positivity rate of S. japonicum in the 13 known endemic villages was 2.7%, and the corresponding seroprevalence was 49.5%. We observed a strong spatial heterogeneity in the families' economic status. S. japonicum infections were more prevalent among the Han than Bai nationality (odds ratio (OR)=3.77, 95% confidence interval (CI)=1.97-7.23) and tobacco growers (OR=3.66, 95% CI=1.77-7.60) and was only found at elevations below 2150 m above sea level. A. lumbricoides and Taenia spp. infections were more prevalent at altitudes above 2150 m when compared to lower settings (OR=1.51, 95% CI=1.24-1.84 and OR=5.32, 95% CI=3.42-8.28, respectively). The opposite was found for T. trichiura (OR=0.31, 95% CI=0.14-0.70). Our findings can guide the design and spatial targeting of control interventions against helminth infections in Eryuan county.

Parasites, people and policy: infectious diseases and the Millennium Development Goals

Here, I briefly review past history and present patterns in the interactions between parasites (defined broadly to include viruses and bacteria along with protozoan, helminth and arthropod parasites) and human populations in developed and developing countries. Against this background, I offer thoughts on current public health initiatives at national and international levels, with particular reference to the Millennium Development Goals. The news is both good and bad: mortality and morbidity from infectious diseases in the developing world are significantly lower than they were 50 years ago, but we should and could be doing better, particularly in relation to neglected tropical diseases.

Understanding the community impact of lymphatic filariasis: a review of the sociocultural literature

Lymphatic filariasis (LF) is endemic in approximately 80 tropical and subtropical countries. About 120 million people are infected with the parasite and a billion are estimated to be at risk of infection. The main focus of the LF elimination programme to date has been to interrupt transmission by means of annual community-wide treatment campaigns with diethylcarbamazine and albendazole, or albendazole and ivermectin, for a period of four to six years. Although substantial progress has been recorded wherever the strategy has been successfully implemented, initial gains have been accompanied by a realization that this strategy alone will not ensure a permanent solution in all settings. The fairly extensive LF literature is dominated by laboratory research and quantitative field measurement of the impact of LF, particularly local prevalence studies of parasite-infected humans and vectors. As the global elimination programme expands, the absence of sociocultural understanding is being recognized as a critical flaw in ensuring that programmes are appropriate and responsive to local needs and understanding. This paper assesses the current state of sociocultural understanding pertaining to LF. It concludes that, at present, there is insufficient understanding of the sociocultural factors associated with the presence and treatment of the disease, and that appropriate social science methods should be used to address this deficiency and ensure community partnership in delivering and sustaining the success of LF elimination programmes.

Neglected tropical diseases in Uganda: the prospect and challenge of integrated control

So-called ‘neglected tropical diseases’ (NTDs) are becoming less neglected, with increasing political and financial commitments to their control. These recent developments were preceded by substantial advocacy for integrated control of different NTDs, on the premise that integration is both feasible and cost-effective. Although the approach is intuitively attractive, there are few countrywide experiences to confirm or refute this assertion. Using the example of Uganda, this article reviews the geographical and epidemiological bases for integration and assesses the potential opportunities for, and operational challenges of, integrating existing control activities for several of these diseases under an umbrella vertical programme.

Neglected tropical diseases

These diseases could be controlled or eliminated in our lifetimes if efforts are better coordinated

Anaemia: a useful indicator of neglected disease burden and control

The authors argue that one way of evaluating the effectiveness of an intervention aimed at controlling neglected tropical diseases would be to assess its impact on anemia prevalence.

A student-led campaign to help tackle neglected tropical diseases

The authors propose that innovative student-led campaigns to address neglected diseases can and do make a practical difference.

Unfulfilled potential: using diethylcarbamazine-fortified salt to eliminate lymphatic filariasis

Fortifying salt with diethylcarbamazine (DEC) is a safe, low-cost and effective strategy to eliminate transmission of lymphatic filariasis. DEC-fortified salt has been used successfully in pilot projects in several countries and has been used operationally by China to eliminate lymphatic filariasis. The successful use of iodized salt to eliminate iodine-deficiency disorders is encouraging; similarly, fortified salt could be used as a vehicle to eliminate lymphatic filariasis. Despite the potential programmatic advantages of fortifying salt with DEC instead of undertaking mass administration of tablets, DEC-fortified salt remains an underutilized intervention. We discuss the reasons for this and suggest settings in which the use of DEC-fortified salt should be considered.

Trachoma: transmission, infection, and control

Mass antibiotic treatment and facial cleanliness are central to WHO's strategy for the elimination of blindness caused by trachoma. Recent studies have highlighted the heterogeneous response of communities to mass treatment and the complex relation between infection with Chlamydia trachomatis and clinical disease. It is important to be able to explain these findings to predict and maximise the effect of treatment on active trachoma disease and blindness in the community. Here we review the immunobiology of trachoma and provide a simple conceptual model of disease pathogenesis. We show how incorporating this model into a mathematical framework leads to an explanation of the observed community distribution of infection, bacterial load, and disease with age. The predictions of the model and empirical data show some differences that underscore the importance of individual heterogeneity in response to infection. The implications of disease transmission and pathogenesis for trachoma control programmes are discussed.

Micronutrient supplements for children after deworming

The availability of a few inexpensive, single-dose drugs to treat soil-transmitted helminths and schistosomiasis offers the potential to reduce a considerable burden of acute disease, especially among children in sub-Saharan Africa. These treatments are being promoted as "rapid impact interventions". However, if helminth infections cause underweight, stunting, anaemia, and impaired mental development in children, how will removing worms alone lead to recovery without treating the underlying deficits that have been caused or made worse by helminth disease? Energy, protein, and micronutrients are required by children who are underweight or who have stunted growth; children who are anaemic will require iron and other micronutrients for haemopoiesis; and children who have lost education will need remedial teaching. Treating neglected worm diseases is an essential first step to good health, but anthelmintic drugs need to be integrated with simple and inexpensive nutritional interventions such as micronutrient supplements to promote recovery and have a rapid effect.

The anthelmintic efficacy of plant-derived cysteine proteinases against the rodent gastrointestinal nematode, Heligmosomoides polygyrus, in vivo

Gastrointestinal (GI) nematodes are important disease-causing organisms, controlled primarily through treatment with synthetic drugs, but the efficacy of these drugs has declined due to widespread resistance, and hence new drugs, with different modes of action, are required. Some medicinal plants, used traditionally for the treatment of worm infections, contain cysteine proteinases known to damage worms irreversibly in vitro. Here we (i) confirm that papaya latex has marked efficacy in vivo against the rodent gastrointestinal nematode, Heligmosomoides polygyrus, (ii) demonstrate the dose-dependent nature of the activity (>90% reduction in egg output and 80% reduction in worm burden at the highest active enzyme concentration of 133 nmol), (iii) establish unequivocally that it is the cysteine proteinases that are the active principles in vivo (complete inhibition of enzyme activity when pre-incubated with the cysteine proteinase-specific inhibitor, E-64) and (iv) show that activity is confined to worms that are in the intestinal lumen. The mechanism of action was distinct from all current synthetic anthelmintics, and was the same as that in vitro, with the enzymes attacking and digesting the protective cuticle. Treatment had no detectable side-effects on immune cell numbers in the mucosa (there was no difference in the numbers of mast cells and goblet cells between the treated groups) and mucosal architecture (length of intestinal villi). Only the infected and untreated mice had much shorter villi than the other 3 groups, which was a consequence of infection and not treatment. Plant-derived cysteine proteinases are therefore prime candidates for development as novel drugs for the treatment of GI nematode infections.

Vaccines against blood-feeding nematodes of humans and livestock

This paper summarises the progress towards vaccine development against the major blood-feeding nematodes of man and livestock, the hookworms and Haemonchus contortus, respectively. The impact of the diseases and the drivers for vaccine development are summarized as well as the anticipated impact of the host immune response on vaccine design. The performance requirements are discussed and progress towards these objectives using defined larval and adult antigens, many of these being shared between species. Specific examples include the Ancylostoma secreted proteins and homologues in Haemonchus as well as proteases used for digestion of the blood meal. This discussion shows that many of the major vaccine candidates are shared between these blood-feeding species, not only those from the blood-feeding stages but also those expressed by infective L3s in the early stages of infection. Challenges for the future include: exploiting the expanding genome information for antigen discovery, use of different recombinant protein expression systems, formulation with new adjuvants, and novel methods of field testing vaccine efficacy.

Urocanic acid is a major chemoattractant for the skin-penetrating parasitic nematode Strongyloides stercoralis

Host-seeking behavior by parasitic nematodes relies heavily on chemical cues emanating from potential hosts. Nonspecific cues for Strongyloides stercoralis, a nematode that infects humans and a few other mammals, include carbon dioxide and sodium chloride; however, the characteristic species specificity of this parasite suggested the existence of other, more specific cues. Here we show that the infective larva of S. stercoralis is strongly attracted to an extract of mammalian skin and that the active component in this skin extract is urocanic acid. Urocanic acid, a histidine metabolite, is particularly abundant in mammalian skin and skin secretions, suggesting that it serves as an attractant specific to mammalian hosts. The attractant activity of urocanic acid is suppressed by divalent metal ions, suggesting a possible strategy for preventing infection.

Lymphatic filariasis elimination in the Pacific: PacELF replicating Japanese success

Japan successfully eliminated lymphatic filariasis and other parasitic diseases through community-driven, integrated nationwide campaigns undertaken during the 1960s and 1970s. The campaigns also created a cadre of experienced clinicians, scientists and public health workers with excellent technical and operational knowledge and a positive attitude towards filariasis elimination. These factors, and the humanitarian desire to improve health in neighbouring nations, influenced Japan to support filariasis control efforts overseas, starting in the 1970s and continuing through to the inception of the Pacific Programme to Eliminate Lymphatic Filariasis (PacELF) in 1999. The unique community-driven, self-help approach of Japan to disease control and health improvement profoundly influenced the activities of PacELF. PacELF is demonstrating that the successful national disease-elimination model in Japan can be extended to the regional level.

Beyond deworming: the promotion of school-health-based interventions by Japan

Deworming bestows a variety of health and socioeconomic benefits and has been embraced by developing countries. To extend the beneficial impact of deworming, the Asian Centre of International Parasite Control (ACIPAC) project has carried out activities to link deworming with health-promoting school programs in the Greater Mekong Subregion (Cambodia, Laos, Myanmar, Thailand and Vietnam). ACIPAC has also conducted an integrated school-health-based program, including deworming and malaria education, under the umbrella of the health-promoting schools initiative. Implementing "beyond-deworming" efforts is now a practical challenge in the subregion.

Lab-on-a-chip devices for global health: past studies and future opportunities

A rapidly emerging field in lab-on-a-chip (LOC) research is the development of devices to improve the health of people in developing countries. In this review, we identify diseases that are most in need of new health technologies, discuss special design criteria for LOC devices to be deployed in a variety of resource-poor settings, and review past research into LOC devices for global health. We focus mainly on diagnostics, the nearest-term application in this field.

Hydrolysis products of cAMP analogs cause transformation of Trypanosoma brucei from slender to stumpy-like forms

African sleeping sickness is a disease caused by Trypanosoma brucei. T. brucei proliferate rapidly in the mammalian bloodstream as long, slender forms, but at higher population densities they transform into nondividing, short, stumpy forms. This is thought to be a mechanism adopted by T. brucei to establish a stable host-parasite relationship and to allow a transition into the insect stage of its life cycle. Earlier studies have suggested a role for cAMP in mediating this transformation. In this study, using membrane-permeable nucleotide analogs, we show that it is not the cAMP analogs themselves but rather the hydrolyzed products of membrane-permeable cAMP analogs that prevent proliferation of T. brucei. The metabolic products are more potent than the cAMP analogs, and hydrolysis-resistant cAMP analogs are not antiproliferative. We further show that the antiproliferative effect of these membrane-permeable adenosine analogs is caused by transformation into forms resembling short, stumpy bloodstream forms. These data suggest that the slender-to-stumpy transformation of T. brucei may not be mediated directly by cAMP and also raise the possibility of using such adenosine analogs as antitrypanosomal drugs.

Intervention for the control of soil-transmitted helminthiasis in the community

The global strategy for the control of soil-transmitted helminthiasis, based on regular anthelminthic treatment, health education and improved sanitation standards, is reviewed. The reasons for the development of a control strategy based on population intervention rather than on individual treatment are explained. The evidence and experience from control programmes that created the basis for (i) the definition of the intervention package, (ii) the identification of the groups at risk, (iii) the standardization of the community diagnosis and (iv) the selection of the appropriate intervention for each category in the community are discussed. How to best deliver the appropriate intervention, the impact of the control measures on morbidity and on indicators such as school attendance, cognitive development and productivity are presented. The factors influencing the cost-benefits of helminth control are also considered. The recent progress on the control of soil-transmitted helminth infections is illustrated. Research needs are analysed in relation to the most recent perceptions from private-public partnerships involved in helminth control. The way forward for the control of soil-transmitted helminth infections is described as a multi-disease approach that goes beyond deworming and fosters a pro-poor strategy that supports the aims of the Millennium Development Goals.

Transmission control for schistosomiasis - why it matters now

Current population-based schistosomiasis treatment programs are a first step to reducing the global burden of Schistosoma-related disease; however, they might not dramatically reduce parasite transmission in highly endemic areas. Consequently, the benefits of these programs remain in doubt because recurring low-level reinfection is likely to be associated with subtle but persistent morbidities such as anemia, undernutrition and diminished performance status. The real health benefits of transmission control need to be reconsidered and attention given to more aggressive and, ultimately, more affordable parasite elimination strategies. The next generation of schistosomiasis control can be optimized using new monitoring tools and effective transmission containment.

A purified Bacillus thuringiensis crystal protein with therapeutic activity against the hookworm parasite Ancylostoma ceylanicum

Crystal (Cry) proteins produced by the soil bacterium Bacillus thuringiensis (Bt) are harmless to vertebrates, but they are highly toxic to insects and nematodes. Their value in controlling insects that destroy crops and transmit human diseases is well established. Although it has recently been demonstrated that a few individual Bt Cry proteins, such as Cry5B, are toxic to a wide range of free-living nematodes, the potential activity of purified Cry proteins against parasitic nematodes remains largely unknown. We report here studies aimed at characterizing in vitro and in vivo anthelminthic activities of purified recombinant Cry5B against the hookworm parasite Ancylostoma ceylanicum, a bloodfeeding gastrointestinal nematode for which humans are permissive hosts. By using in vitro larval development assays, Cry5B was found to be highly toxic to early stage hookworm larvae. Exposure of adult A. ceylanicum to Cry5B was also associated with significant toxicity, including a substantial reduction in egg excretion by adult female worms. To demonstrate therapeutic efficacy in vivo, hamsters infected with A. ceylanicum were treated with three daily oral doses of purified Cry5B, the benzimidazole anthelminthic mebendazole, or buffer. Compared with control (buffer-treated) animals, infected hamsters that received Cry5B showed statistically significant improvements in growth and blood hemoglobin levels as well as reduced worm burdens that were comparable to the mebendazole-treated animals. These data demonstrate that Cry5B is highly active in vitro and in vivo against a globally significant nematode parasite and that Cry5B warrants further clinical development for human and veterinary use.

Human schistosomiasis

Schistosomiasis or bilharzia is a tropical disease caused by worms of the genus Schistosoma. The transmission cycle requires contamination of surface water by excreta, specific freshwater snails as intermediate hosts, and human water contact. The main disease-causing species are S haematobium, S mansoni, and S japonicum. According to WHO, 200 million people are infected worldwide, leading to the loss of 1.53 million disability-adjusted life years, although these figures need revision. Schistosomiasis is characterised by focal epidemiology and overdispersed population distribution, with higher infection rates in children than in adults. Complex immune mechanisms lead to the slow acquisition of immune resistance, though innate factors also play a part. Acute schistosomiasis, a feverish syndrome, is mostly seen in travellers after primary infection. Chronic schistosomal disease affects mainly individuals with long-standing infections in poor rural areas. Immunopathological reactions against schistosome eggs trapped in the tissues lead to inflammatory and obstructive disease in the urinary system (S haematobium) or intestinal disease, hepatosplenic inflammation, and liver fibrosis (S mansoni, S japonicum). The diagnostic standard is microscopic demonstration of eggs in the excreta. Praziquantel is the drug treatment of choice. Vaccines are not yet available. Great advances have been made in the control of the disease through population-based chemotherapy but these required political commitment and strong health systems.

Praziquantel for the treatment of schistosomiasis: its use for control in areas with endemic disease and prospects for drug resistance

Praziquantel became available for the treatment of schistosomiasis and other trematode-inflicted diseases in the 1970s. It was revolutionary because it could be administered orally and had very few unwanted side effects. As a result of marked reductions in the price of praziquantel, the rate at which it is used has accelerated greatly in recent years. For the foreseeable future it will be the mainstay of programs designed to control schistosome-induced morbidity, particularly in sub-Saharan Africa where schistosomiasis is heavily endemic. There is currently no evidence to suggest that any schistosomes have developed resistance to praziquantel as a result of its widespread use. Nevertheless, while resistance may not pose an obvious or immediate threat to the usefulness of praziquantel, complacency and a failure to monitor developments may have serious consequences in the longer term since it will be the only drug that is readily available for large-scale treatment of schistosomiasis.

The antipoverty vaccines

The neglected tropical diseases represent a group of parasitic and bacterial diseases, occurring primarily in rural areas or impoverished urban areas of developing countries. Because of their chronic and stigmatizing character and their impact on child development, pregnancy outcomes, and worker productivity, the neglected tropical diseases are considered poverty-promoting conditions. Through the activities of public-private partnerships, first or second-generation recombinant vaccines for three of these conditions--hookworm, leishmaniasis, and schistosomiasis, have undergone early development and clinical testing. However, through the acquisition of extensive bioinformatics information or animal model testing for several other neglected tropical diseases pathogens, it is possible to consider new generation vaccines as well for amebiasis, Buruli ulcer, Chagas disease, Chlamydia infections (including trachoma), leprosy, leptospirosis, and the treponematoses. Early development of such antipoverty vaccines will require the establishment of product development public-private partnerships and partnerships with innovative developing countries where these diseases are endemic.

Reconsidering the underestimated burden caused by neglected tropical diseases

It is generally acknowledged that the burden caused by neglected tropical diseases needs to be reassessed. Not only are there several important diseases unaccounted for, but new information suggests they have a more substantial impact on health than initially thought. Looking at the tropical diseases as a group makes sense: they tend to cluster in the same poor populations and, to make progress with their control, they will have to be dealt with in an integrated manner. Measuring the effect of such integrated control is likely to reveal the real impact of tropical diseases on human health and wellbeing.

Projected benefits from integrating NTD programs in sub-Saharan Africa

The integration of preventive chemotherapy programs (PCPs) targeting multiple neglected tropical diseases (NTDs) with similar strategic approaches offers opportunities for enhanced cost-effectiveness. To estimate the potential cost savings and health outcomes of integrated programs, the data available for five NTDs (lymphatic filariasis, onchocerciasis, intestinal helminthiasis, schistosomiasis and trachoma) can be used to define eligible target populations, the probable overlap of at-risk populations, and the cost per person treated in stand-alone and integrated programs. If all targets for 2006 in sub-Saharan Africa are met, then savings of 26-47% can be projected from such integration (a cost of US dollar 58-81 million versus dollar 110 million for stand-alone PCPs). These first estimates can be refined as empirical data become available from integrated PCPs in the future.

A blueprint for success: integration of neglected tropical disease control programmes

The rapid expansion of chemotherapy-based control programmes for neglected tropical diseases has been catalysed by funding from the Bill and Melinda Gates Foundation, donations of several drugs from pharmaceutical manufacturers, and the reduced price of the drug praziquantel. Focussing on lymphatic filariasis, schistosomiasis and soil-transmitted helminthiasis, we review here the progress made to date with the implementation and integration of large-scale control programmes. Unresolved issues include a means for rapid identification of communities at highest risk of co-morbidity, cost-effective approaches for integrating the technical interventions into setting-specific packages, and determination of the most appropriate and sustainable delivery systems.

New technologies for the control of human hookworm infection

Since the 1990s, the major approach to hookworm control has been morbidity reduction in school-aged children by periodic deworming with benzimidazoles. Now, efforts are underway to determine the feasibility of integrating deworming with control programs that target other neglected tropical diseases. However, the sustainability of benzimidazole deworming for hookworm is of concern because of the variable efficacy of mebendazole, high rates of post-treatment reinfection and possible development of drug resistance. This requires parallel efforts to develop new and complementary hookworm control tools, such as new anthelmintic drugs (e.g. tribendimidine) and a recombinant hookworm vaccine. It is hoped that, ultimately, anthelmintic vaccination will be linked to deworming as part of an expanded control package.

Implementation of national schistosomiasis control programmes in West Africa

Burkina Faso, Mali and Niger are countries endemic for schistosomiasis, with a high predominance of Schistosoma haematobium. With the support of the Bill and Melinda Gates Foundation through the Schistosomiasis Control Initiative, national control programmes were launched in these countries in 2004. Here, we describe the progress of implementation for each programme and the challenges for maintaining sustainability for schistosomiasis control in these countries.

Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm

The three main soil-transmitted helminth infections, ascariasis, trichuriasis, and hookworm, are common clinical disorders in man. The gastrointestinal tract of a child living in poverty in a less developed country is likely to be parasitised with at least one, and in many cases all three soil-transmitted helminths, with resultant impairments in physical, intellectual, and cognitive development. The benzimidazole anthelmintics, mebendazole and albendazole, are commonly used to remove these infections. The use of these drugs is not limited to treatment of symptomatic soil-transmitted helminth infections, but also for large-scale prevention of morbidity in children living in endemic areas. As a result of data showing improvements in child health and education after deworming, and the burden of disease attributed to soil-transmitted helminths, the worldwide community is awakening to the importance of these infections. Concerns about the sustainability of periodic deworming with benzimidazole anthelmintics and the emergence of resistance have prompted efforts to develop and test new control tools.

An integrated approach for risk profiling and spatial prediction of Schistosoma mansoni-hookworm coinfection

Multiple-species parasitic infections are pervasive in the developing world, yet resources for their control are scarce. We present an integrated approach for risk profiling and spatial prediction of coinfection with Schistosoma mansoni and hookworm for western Côte d'Ivoire. Our approach combines demographic, environmental, and socioeconomic data; incorporates them into a geographic information system; and employs spatial statistics. Demographic and socioeconomic data were obtained from education registries and from a questionnaire administered to schoolchildren. Environmental data were derived from remotely sensed satellite images and digitized ground maps. Parasitologic data, obtained from fecal examination by using two different diagnostic approaches, served as the outcome measure. Bayesian variogram models were used to assess risk factors and spatial variation of S. mansoni-hookworm coinfection in relation to demographic, environmental, and socioeconomic variables. Coinfections were found in 680 of 3,578 schoolchildren (19.0%) with complete data records. The prevalence of monoinfections with either hookworm or S. mansoni was 24.3% and 24.1%, respectively. Multinomial Bayesian spatial models showed that age, sex, socioeconomic status, and elevation were good predictors for the spatial distribution of S. mansoni-hookworm coinfection. We conclude that our integrated approach, employing a diversity of data sources, geographic information system and remote sensing technologies, and Bayesian spatial statistics, is a powerful tool for risk profiling and spatial prediction of S. mansoni-hookworm coinfection. More generally, this approach facilitates risk mapping and prediction of other parasite combinations and multiparasitism, and hence can guide integrated disease control programs in resource-constrained settings.

Priority setting and the 'neglected' tropical diseases

In this paper David Canning argues that interventions against 'neglected' tropical diseases should be thought of as investments in human capital and form an integral part of global poverty reduction. He argues that overall burden of disease should not be the criterion for priority setting; if the goal is to maximize health benefits from a fixed health budget then cost-effective interventions should be prioritized. Whilst many people find objectionable the assignment of a monetary value to health, a cost-benefit approach, combining health and economic benefits, would allow the health sector to present arguments to policy makers, based on the rate of return on investment. Since many health interventions in low-income countries have exceptionally high rankings in terms of cost-benefit ratios, this should result in large flows from other sectors to the health sector.

Control of Human Parasitic Diseases: Context and Overview

The control of parasitic diseases of humans has been undertaken since the aetiology and natural history of the infections was recognized and the deleterious effects on human health and well-being appreciated by policy makers, medical practitioners and public health specialists. However, while some parasitic infections such as malaria have proved difficult to control, as defined by a sustained reduction in incidence, others, particularly helminth infections can be effectively controlled. The different approaches to control from diagnosis, to treatment and cure of the clinically sick patient, to control the transmission within the community by preventative chemotherapy and vector control are outlined. The concepts of eradication, elimination and control are defined and examples of success summarized. Overviews of the health policy and financing environment in which programmes to control or eliminate parasitic diseases are positioned and the development of public-private partnerships as vehicles for product development or access to drugs for parasite disease control are discussed. Failure to sustain control of parasites may be due to development of drug resistance or the failure to implement proven strategies as a result of decreased resources within the health system, decentralization of health management through health-sector reform and the lack of financial and human resources in settings where per capita government expenditure on health may be less than $US 5 per year. However, success has been achieved in several large-scale programmes through sustained national government investment and/or committed donor support. It is also widely accepted that the level of investment in drug development for the parasitic diseases of poor populations is an unattractive option for pharmaceutical companies. The development of partnerships to specifically address this need provides some hope that the intractable problems of the treatment regimens for the trypanosomiases and leishmaniases can be solved in the not too distant future. However, it will be difficult to implement and sustain such interventions in fragile health services often in settings where resources are limited but also in unstable, conflict-affected or post-conflict countries. Emphasis is placed on the importance of co-endemicity and polyparasitism and the opportunity to control parasites susceptible to cost-effective and proven chemotherapeutic interventions for a package of diseases which can be implemented at low cost and which would benefit the poorest and most marginalized groups. The ecology of parasitic diseases is discussed in the context of changing ecology, environment, sociopolitical developments and climate change. These drivers of global change will affect the epidemiology of parasites over the coming decades, while in many of the most endemic and impoverished countries parasitic infections will be accorded lower priority as resourced stressed health systems cope with the burden of the higher-profile killing diseases viz., HIV/AIDS, TB and malaria. There is a need for more holistic thinking about the interactions between parasites and other infections. It is clear that as the prevalence and awareness of HIV has increased, there is a growing recognition of a host of complex interactions that determine disease outcome in individual patients. The competition for resources in the health as well as other social sectors will be a continuing challenge; effective parasite control will be dependent on how such resources are accessed and deployed to effectively address well-defined problems some of which are readily amenable to successful interventions with proven methods. In the health sector, the problems of the HIV/AIDS and TB pandemics and the problem of the emerging burden of chronic non-communicable diseases will be significant competitors for these limited resources as parasitic infections aside from malaria tend to be chronic disabling problems of the poorest who have limited access to scarce health services and are representative of the poorest quintile. Prioritization and advocacy for parasite control in the national and international political environments is the challenge.

Incorporating a rapid-impact package for neglected tropical diseases with programs for HIV/AIDS, tuberculosis, and malaria

Hotez et al. argue that achieving success in the global fight against HIV/AIDS, tuberculosis, and malaria may well require a concurrent attack on the neglected tropical diseases.

Control of neglected tropical diseases: integrated chemotherapy and beyond

Utzinger and de Savigny discuss the implications of a new policy paper, which argues that the control of "the big three" diseases (HIV, TB, and malaria) should be integrated with control of the neglected tropical diseases.

The burden of non communicable diseases in developing countries

BACKGROUND: By the dawn of the third millennium, non communicable diseases are sweeping the entire globe, with an increasing trend in developing countries where, the transition imposes more constraints to deal with the double burden of infective and non-infective diseases in a poor environment characterised by ill-health systems. By 2020, it is predicted that these diseases will be causing seven out of every 10 deaths in developing countries. Many of the non communicable diseases can be prevented by tackling associated risk factors. METHODS: Data from national registries and international organisms are collected, compared and analyzed. The focus is made on the growing burden of non communicable diseases in developing countries. RESULTS: Among non communicable diseases, special attention is devoted to cardiovascular diseases, diabetes, cancer and chronic pulmonary diseases. Their burden is affecting countries worldwide but with a growing trend in developing countries. Preventive strategies must take into account the growing trend of risk factors correlated to these diseases. CONCLUSION: Non communicable diseases are more and more prevalent in developing countries where they double the burden of infective diseases. If the present trend is maintained, the health systems in low-and middle-income countries will be unable to support the burden of disease. Prominent causes for heart disease, diabetes, cancer and pulmonary diseases can be prevented but urgent (preventive) actions are needed and efficient strategies should deal seriously with risk factors like smoking, alcohol, physical inactivity and western diet.